Abstract
We have developed a non-wearing type of pupillography with better temporal and spatial resolution than conven-tional devices. The subject lies on a comfortable bed, where his/her head is supported by a soft pillow, and looks into the pupillographic device. A video camera sensitive to infrared light is positioned about 70cm from the participant's eye and the video image is digitized at 125Hz with a resolution of 2μm diameter utilizing recent developments in high-speed electronic counters. To test the applicability of this new device, we investigated the association of pupillographic measurements with sleepiness under the condition of sleep deprivation. In nine physically and mentally healthy young subjects, physiological arameters were recorded every 2hr in an overnight sleep-deprived setting. As papillary measures, spontaneous pupillary movements were recorded continuously for a period of 4.096 seconds with the pupillography at 125Hz. Two parameters are calculated to describe the pupil behavior: average size of the pupil and pre-determined index reflecting the fluctuation of the pupil size. The effect of length of sleep deprivation on these two parameters was analyzed. While the length of sleep deprivation had no significant effect on the average pupil size, it had a significant effect on the index of pupil fluctuation: the level of fluctuation increased gradually during the course of overnight sleep deprivation. These results are in good accordance with previous reports in literature, although we analyzed the component of higher frequency regarding the pupil size fluctuation as compared to previous studies. This preliminary study provides evidence that this pupillography is reliably applicable to physiological studies with multiple measurements. It is expected that the non-invasive nature of this device will allow its use in a broad range of clinical studies as well.
